More than 100 000 people have been forced to flee their homes as an unprecedented number of large wildfires burn in the forests of Canada this year. On Monday 12 June 2023 a total of 449 separate fires were reportedly burning, 219 of which were considered to be out of control. The country has already lost 48 000 km² of forest to fires this season, an area larger than Maryland, the Netherlands, or Guinea Bissau. Air pollution caused by the fires has affected cities across Canada and the northern United States, with Detroit and New York both briefly holding the title of the world cities with the worst air quality.
The fires have widely been linked to rising global temperatures, with the government of Justin Trudeau coming under fire for a failure to address the climate crisis properly. Canada is currently suffering significantly warmer and drier weather than would have been considered normal a few decades ago and. like many parts of the world, has consistently been having exceptionally warm summers since the mid 1990s, with a general upward trend in summer temperatures. To make matters worse, this year an El Niño weather system is thought to be developing over the South Pacific, which would be expected to bring warmer weather to much of Canada even in the absence of a rising trend, and which is expected to drive the temperature this summer significantly higher than in recent years.
The El Niño is the warm phase of a long-term climatic oscillation affecting the southern Pacific, which can influence the climate around the world. The onset of El Niño conditions is marked by a sharp rise in temperature and pressure over the southern Indian Ocean, which then moves eastward over the southern Pacific. This pulls rainfall with it, leading to higher rainfall over the Pacific and lower rainfall over South Asia. This reduced rainfall during the already hot and dry summer leads to soaring temperatures in southern Asia, followed by a rise in rainfall that often causes flooding in the Americas and sometimes Africa. Worryingly climatic predictions for the next century suggest that global warming could lead to more frequent and severe El Niño conditions, extreme weather conditions a common occurrence.
However, this is not the whole story; with many in Canada also questioning the roe played by the country's timber industry in driving the crisis. Many areas in Canada which were once covered by old-growth mixed temperate forests are now home to large stands of a single type of tree, typically fast-growing and straight-trunked Conifers such as Pines. These trees are profitable for the timber industry, as their wood is straight, of a predicable quality, and produced relatively rapidly, but are particularly prone to fires.
Many Conifers, including Pines, are fire-adapted trees which are able to take advantage of forest fires. The trees themselves may be destroyed in a fire, but their seeds, held within protective, fire-resilient cones, will tend to survive, and can grow rapidly on newly cleared ground (the trait that makes them attractive to commercial foresters), enabling them to shade out slower growing species. However, in a natural environment stands of Conifers tend to be of limited size, and interspersed with stands of other trees, limiting the ability of fires to spread. Conifer plantations can comprise vast areas of land covered by a single species of tree, enabling fire to spread freely. Worse still, Conifers are able to grow closer together than most tree types, which is advantageous to the trees without any major impact on the wider forest where they are self-seeding, and their distribution is essentially random, but when Humans become involved and start planning the maximum number of trees that can be grown on an area of ground, the result is typically a vast area of closely packed trees, which creates a perfect environment for fire to spread.
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